GB1562938A - Fluid diode - Google Patents

Description

PATENT SPECIFICATION

( 11) 1562938 ( 21) Application No 45408/77 ( 22) Filed 1 Nov 1977 ( 19) ( 31) Convention Application No 7 612 384 ( 32) Filed 8 Nov 1976 in Add ( 33) Netherlands (NL) I I ( 44) Complete Specification published 19 March 1980 ( 51) INT CL 5 F 16 K 15/04 ( 52) Index at acceptance F 2 V El M J 5 ( 54) IMPROVEMENTS IN OR RELATING TO A FLUID DIODE ( 71) We, B V NERATOOM, a Dutch body corporate of Laan van Nieuw Oost Indi U 129-135, 's-Gravenhage, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in

and by the following statement:-

The invention relates to a fluid diode comprising a through-flow chamber connecting at least one inlet pipe to at least one outlet pipe, the through-flow chamber having a diameter larger than that of the inlet pipe.

i 5 There are known various types of check valves, among which may be reckoned also fluid diodes, inter alia those incorporating a ball Such check valves are so constructed that a normal through-flow of fluid from the inlet to the outlet is not impeded, but that in case of a reverse flow the ball acts to shut off the inlet.

Check valves are employed in all kinds of systems wherein an undesirable reverse flow is possible Some of these systems are subjected to severe security regulations An example of such a system is the heat transport system of a sodium-cooled nuclear reactor In order to be able to cope with failures, such a system consists of a number of separate parallel loops, each comprising a pump, heat exchanger and check valve of its own If one of the pump fails, the other loops can cope with the heat transport.

For that purpose it should be ensured, however, that not a great portion of the transport medium flows through the defective loop Conventional check valves, including those comprising a ball, may fail, for example because the ball remains stuck in a position where it does not shut off the inlet.

It is the object of the invention to provide a fluid diode which with absolute certainty reduces the reverse flow to an acceptable quantity by a strongly increased flow resistance.

According to the invention, this obiect is effected by providing in the through-flow chamber a plurality of balls movable randomly within a space defined between two grids, the grids being so constructed that on flow of fluid in the direction of the inlet the balls shut off almost completely fluid flow through the grid on the inlet side whereas on flow in the direction of the outlet the balls cannot shut off fluid flow through the grid on the outlet side.

Owing to the construction of the present fluid diode using a relatively great number of balls it is possible with absolute certainty to prevent the complete backflow of the flowing medium, because although perhaps one single ball may remain stuck, by far the greater part will certainly not.

Various embodiments of the grids are conceivable, as a result of which the grid on the inlet side, in case of a flow from the through-flow chamber into the direction of the inlet, can be shut off almost completely by the balls, and the grid at the side of the outlet, in case of normal flow, cannot be shut off by the balls Preferably there are employed flat grids, the grid at the outlet side having a larger surface than the other grid It is also possible to construct the grid at the outlet side as a perforated plate provided with bulbs of different height in such a manner that the grid cannot be shut off by the balls.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig 1 is a schematic cross-section of a fluid diode according to the invention, showing the situation of a normal flow from the inlet in the direction of the arrow, Fig 2 is a schematic cross-section of a fluid diode according to the invention, showing the situation of a reverse flow in the direction of the arrow, and Fig 3 shows schematically a multiple loop reactor system, in which the fluid diode according to the invention can be employed.

Description of Figs 1 and 2 95

The fluid diode consists of an enclosed chamber ( 1) of a cylindrical shape connected to an entrance nozzle ( 2) and an exit nozzle ( 3) by two cones ( 7) and ( 8), respectively, and forming an apparatus 100 it' 1,562,938 through which a gas or fluid can flow by connecting same to a piping system by means of nozzles ( 2) and ( 3).

Within the chamber ( 1) there is positioned a grid ( 5) while in the entrance nozzle ( 2) there is positioned another grid ( 4), the diameter of which is smaller than the former.

In this way there is formed between the two grids ( 4) and ( 5) a spearate chamber ( 9) wherein are placed a number of balls ( 6), the diameter of which is larger than the diameter of the holes in the grids In this manner the balls are captured between the two grids ( 4) and ( 5) of chamber ( 1).

The density of each ball be either less than: equal to or more than that of the fluid passing through the apparatus Diameter "A" of the chamber ( 1) is larger than the connecting nozzle diameters "B" of nozzles ( 2) and ( 3).

Working of the apparatus In Fig 1 the apparatus is connected to a piping system at the connecting ends ( 2) and ( 3) while a fluid passes through the chamber ( 1) fnormal flow direction) The balls ( 6) in chamber ( 9) are moved in the upward direction against grid ( 5) and are held there in that position The number of holes in the grid ( 5) is much greater than the number of balls ( 6) while the flow passage over the balls and through the holes in grid ( 5) is relatively easy and causes little flow resistance to the fluid.

If the fluid flow reverses as shown in Fie 2, the florid will move the balls downwards until they are stopped by grid ( 4) in nozzle ( 2) where the balls are collected, however, in a now much smaller flow passage above the smaller grid ( 4) In this sitnation the balls are stacked on top of each other forming a rather large flow resistance to the reversing flow.

The total pressure drop of the apparatus during the reversed flow situation as shown -in Fig 2 can be a multinle value of the pressure drop in the normal flow direction (Fig 1) Theoretically any ratio between pressure drop in the reverse flow relative to thp normal flow direction can be reached, while in practical terms a ratio of 100 or better is possible.

Application (Fig 3) An example wherein the fluid diode can be annlied is a mliltinle loon reactor svstem as commonly used for the liquid Metal Fast Breeder Reactor, wherein the entrance chamber to the reactor is fed by two or more parallel sodinm loons to cool the nuclear core ( 13) The normal direction of flow in the sodium loons is indicated by means of arrows Each of these parallel loons normallv contains a pum 1 D ( 10) a check valve ( 11) and a heat exchanger ( 12).

In case one of the pumps in a two-loop system fails to operate under power conditions of the reactor, the other pump alone needs to be able to cool the core while in addition the check valve in the failed loop needs to be closed In case also the check valve in the failed loop does not function properly, there is a risk that the flow from the operating pump by-passes the core through the failed loop In that case the core will be overheated and may melt down, which could be catastrophic.

An example of such a system is shown diagrammatically in Fig 3.

For this application it is imperative that there are used check valves that cannot fail The normal check valves presently known in general consist of a single body in a fluid stream which allows the flow to pass in one direction, but does not permit the flow to reverse, when the valve operates correctly However, in practice it appears that for all practical valves the single body to prevent flow reversal often freezes in the open position and does not close when necessary.

In the present fluid diode there are used a multiple of relatively small balls, of which it is very unlikely that they will all freeze in one position Therefore, the fluid diode will be more reliable for systems of which the safety is of utmost importance.

Typical dimensions The size of the apparatus is not limited 100 and will be determined by the system for which it is used and by the desired characteristics The diameter "A" of the chamber ( 1) would in general be at least two times the diameter "B" of the inlet and outlet 105 pipes ( 2) and ( 3) The diameter "B" will be determined by the allowable flow velocity, which for a sodium system maximally will be in the order of 30 ft/sec, while the cross-section of the open area in the grids 110 need be maximized to minimize pressure drop in the normal flow direction The size of the balls and the weight thereof are determined by the required characteristics of the fluid diode for the system in which it 115 is operating The balls may differ from one another in size and/or weight.

An extensive development program will be required to optimize the dimensions of the apparatus and to determine its charac 120 teristics.

Claims (6)

WHAT WE CLAIM IS:-

1 A fluid diode comprising a throughflow chamber connecting at least one inlet 125 pipe to at least one outlet pipe, the thronuhflow chamber having a diameter greater than that of the inlet pipe and containing a plurality of balls movable randomly within a space defined between two grids, the grids 130 1,562,938 being so constructed that on flow of fluid in the direction of the inlet the balls shut off almost completely fluid flow through the grid on the inlet side whereas on flow in the direction of the outlet the balls cannot shut off fluid flow through the grid on the outlet side.

2 A fluid diode according to claim 1, in which the grids are flat and the grid at the outlet side has a larger surface than the grid at the inlet side.

3 A fluid diode according to claim 2, in which the smaller grid is positioned at the junction of the inlet pipe with the through-flow chamber.

4 A fluid diode according to claim 2 or claim 3, in which the larger grid is positioned where the diameter of the throughflow chamber is largest.

A fluid diode according to any one of claims 1 to 4, in which the balls differ in size and/or weight.

6 A fluid diode constructed, arranged and adapted to operate substantially as described with reference to, and as shown in, Figures 1 and 2 of the accompanying drawings.

MATHYS & SQUIRE, Chartered Patent Agents, Fleet Street, London, EC 4 Y l AY.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd -1980.

Published at The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.